Raman spectroscopic measurements of various hydrogen bearing clathrate hydrates have been performed under high (< 1cm-1) and low resolution (>2 cm-1) conditions. Raman bands for hydrogen in most common clathrate hydrate cavities have been assigned. Unlike most clathrate hydrate guests, the general observation is no longer valid that the larger the clathrate cavity in which a guest resides, the lower the vibrational frequency. This is rationalized by the multiple hydrogen occupancies in larger clathrate cavities. Both the roton and vibron bands for hydrogen clathrates illuminate interesting quantum dynamics of the enclathrated hydrogen molecules. At 77K, the progression from ortho to para H2 occurs over a relatively slow time period (days). The para contribution to the roton region of the spectrum exhibits the triplet splitting also observed in solid para H2. The complex vibron region of the Raman spectrum has been interpreted by observing the change in population of these bands with temperature and with isotopic substitution by deuterium. Raman spectra from H2 and D2 hydrates suggest that the occupancy patterns between the two hydrates are analogous. The Raman measurements demonstrate that this is an effective and convenient method to determine the relative occupancy of hydrogen molecules in different clathrate cavities.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/1145 |
| Date | 07 1900 |
| Creators | Strobel, Timothy A., Koh, Carolyn A., Sloan, E. Dendy |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Rights | Sloan, E. Dendy; Koh, Carolyn A.; Sum, Amadeu |
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